Occipital plate and rod system

Abstract

The present invention has a plate and rod assembly for implantation in the cervical region of the spine which includes an occipital plate having an angled anchor bridging area that is attached to the lower posterior curve of the skull. On either side the bridging area is connected to offset legs which join flanged areas having a high friction surface and which include tethered rod anchors having rod-receiving channels. These flanges include undercut slots longer in one direction than the other to capture the side plates integral to the open U-shaped members including the rod-receiving channels. The side plates extend longer in the direction of the longitudinal axis of the rod when it is in the channel so that they can thus be lowered into the slot and rotated by 90 degrees to capture the channels in the flanges. The channels are closed by a capnut which has a bottom annular flange that also helps to lock the rod in place. The angle of the rod-receiving flanges relative to the plate bridging area allows the rods to be positioned close to the cervical vertebrae so that they can also be attached to the cervical vertebrae using vertebral anchors. The capnut is self-aligning and includes a visual alignment cue that helps to inhibit cross threading by indicating the proper side for starting the capnut on the threads of the channel. Three debossed dots show the alignment relative to a similarly placed set of dots on the proper side of the rod-receiving channel.

1. A spinal rod assembly comprising a rod and an attachment plate having at least one rod anchor which is a U-shaped member having two upright legs that define a rod-receiving channel, the rod-receiving channel having an outwardly extending side plate, the attachment plate having a bridge area defining a plane and the attachment plate further including a first flange and a second flange, the first flange being attached to a first leg which is offset from the bridge area and the first flange being offset from the first leg; and a second flange being attached to a second leg which is offset from the bridge area and the second flange being offset from the second leg, each flange including one of the rod anchors and each flange defining a flange plane and neither flange plane being co-planar with the plane of the bridge member and each of the first and the second flange includes a recess which retains the side plate of the rod-receiving channel and the flange having a high friction surface which directly contacts the rod when the rod is in the rod-receiving channel. 
     
     
       2. A spinal implant assembly as set forth in  claim 1  wherein the high friction surface includes points. 
     
     
       3. A spinal implant assembly as set forth in  claim 2  wherein the high friction surface is knurled. 
     
     
       4. A spinal implant assembly as set forth in  claim 1  wherein the bridge area defines a plane and has screw holes and the flanges independently define their own planes neither of which are in the same plane as the bridge area. 
     
     
       5. A spinal rod assembly including a rod, a rod anchor and a plate for attachment to an occipital portion of a skull wherein the rod anchor has a U-shaped anchor member with a central vertical axis and which defines a rod-receiving channel for the rod and has an extension member extending in a direction transverse to the central vertical axis and in the direction of the rod-receiving channel to define an extension member length and the anchor member having an anchor member width in the direction transverse to the direction of the extension member, the plate having an upper surface and an opposing lower surface and including a slot extending between the upper and the lower surfaces which surrounds the anchor member, the slot defining a slot width and a slot length, the extension member length being longer than the slot width and the anchor member width being shorter than the slot width so that the anchor member can be inserted into the slot from a direction extending from the upper surface to the lower surface and rotated to capture the anchor member in the slot by means of the extension member when the rod-receiving channel is in its final alignment. 
     
     
       6. A spinal rod assembly as set forth in  claim 5  wherein the extension member comprises a side plate. 
     
     
       7. A spinal rod assembly as set forth in  claim 6  wherein the anchor member includes two opposing side plates. 
     
     
       8. A spinal rod assembly as set forth in  claim 7  wherein the anchor member includes threads and a compression member that holds the rod in place in the rod-receiving channel. 
     
     
       9. A spinal rod assembly as set forth in  claim 8  wherein the slot includes two recesses which are defined by undercut areas along the sides of the slot. 
     
     
       10. A spinal rod assembly as set forth in  claim 7  wherein the threads are external threads and the compression member is a cap or a nut or a capnut. 
     
     
       11. A spinal rod assembly as set forth in  claim 10  wherein the rod anchor has a bottom surface which includes a boss that helps to limit the movement of the rod anchor relative to the slot. 
     
     
       12. A spinal rod assembly as set forth in  claim 11  wherein the assembly includes screws, and the plate has a flange which includes the slot and a bridging area with through bores which receive the screws to enable the assembly to be capable of being attached to the skull, and wherein the bridging area is shaped to be placed cranially on the skull relative to the flange. 
     
     
       13. A spinal rod assembly comprising a rod, a rod anchor and an attachment plate having at least two rod anchors each of which comprises a U-shaped member having two upright legs that define a rod-receiving channel, the attachment plate including a bridge area having screw holes and defining a plane and the attachment plate further including a first flange and a second flange, the first flange being attached to a first leg which is offset from the bridge area and the first flange being offset from the first leg; and a second flange being attached to a second leg which is offset from the bridge area and the second flange being offset from the second leg, each flange including one of the rod anchors and each flange defining a flange plane and neither flange plane being co-planar with the plane of the bridge member. 
     
     
       14. A spinal rod assembly as set forth in  claim 13  wherein U-shaped member having two upright legs and the anchor further has an outwardly extending side plate, the attachment plate including a recess that retains the side plate. 
     
     
       15. A spinal rod assembly as set forth in  claim 14  wherein the recess is formed in a flange of the attachment plate that has an upper surface that is a high friction surface. 
     
     
       16. A spinal implant assembly as set forth in  claim 15  wherein the high friction surface includes points. 
     
     
       17. A spinal implant assembly as set forth in  claim 13  wherein the two upright legs are threaded and the assembly further includes a threaded locking member that cooperates with the threads on the upright legs to hold the rod in the channel, and wherein the locking member is a capnut and the channel and the capnut each have a top surface with a visual indicator for the proper starting alignment of the locking member. 
     
     
       18. A spinal implant as set forth in  claim 17  wherein the channel includes external threads and the locking member includes internal threads. 
     
     
       19. A spinal implant assembly as set forth in  claim 18  wherein the visual indication comprises a debossed dot. 
     
     
       20. A spinal implant assembly as set forth in  claim 19  wherein the visual indication comprises a series of dots.